How Motorcycle Alternators Work
A motorcycle alternator generates power and helps keep the battery charged. Matt Bochnak from HowToMotorcycleRepair.com provides an inside look at motorcycle alternators and the physics behind how they work in this video.
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-[MATT] Hey what’s up everyone, it’s Matt from HowToMotorcycleRepair.com. In this video, we are going to talk about one basic part on a motorcycle: the alternator.
The alternator’s main function is to generate power for all electrical accessories, and to keep the battery charged during motorcycle operation.
Some motorcycles have alternators that look very similar to those found on cars. These alternators have a rotor, stator and voltage regulator all packaged in one unit. On a motorcycle, the alternator is powered by gears, whereas on a car it is belt driven.
On other motorcycles, the rotor and stator are located on the engine, and the voltage regulator is located elsewhere on the frame due to space constraints. Since the voltage regulator is separate, sometimes people simply refer to the alternator as the “rotor and stator.” This is the most common arrangement found on motorcycles.
The rotor and stator are typically located on one end of the crankshaft, either on the left or right-hand side, and housed in an engine cover.
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Removing the engine cover reveals the rotor and stator. The stator is bolted to the engine cover, and as the name implies, it “stays” in place. The rotor, on the other hand, rotates when the engine is running.
OK, so let’s go over some simple physics on how these components work.
You may remember learning about Faraday’s law in school. It states that moving a magnet through a coil of wire will “induce” voltage into the coil. This magnet can be moved in and out, or even rotated.
Another science experiment you may recall is creating a simple electromagnet. Wrapping a coil of wire over a nail, and then applying battery power, will turn these parts into a low-powered magnet. You can even pick up small objects like paper clips.
So, let’s see how these two simple principles apply to the motorcycle components.
This particular alternator has a third component, the field coil, which is also stationary. This is a coil of wire similar to the one wrapped around the nail you saw earlier. The rotor acts like the nail in the experiment. So, when battery voltage is applied to the field coil, the rotor becomes a large electromagnet.
Also, notice the unique shape of the rotor. This shape allows the poles of the magnet to be arranged in an alternating fashion.
Now, let’s go back to Faraday’s law. If we rotate the rotor, which is now a magnet, voltage is created and power is produced in the stator, which is a coil or wire loop.
So, that is basically how a motorcycle alternator works.
Alright, I hope you enjoyed this video on how a motorcycle alternator works.
If you’d like to see more of my videos, head over to HowToMotorcycleRepair.com, or check out my YouTube channel, MatthewMCrepair. I’m also on Facebook and Twitter. Thanks for watching and see you next time.
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